The present invention relates to piezoelectric relays and more particularly to piezoelectric relays arranged as a matrix switch.
Heretofore, matrix switches, particularly those adapted for telecommunication applications, have typically been implemented using electromagnetic relays. Over the years, improvements in electromagnetic relay designs have resulted in increased efficiency and reduced physical size. Nevertheless, such relays have their drawbacks. They are relatively complex and expensive to manufacture. Their operating coils require a multitude of turns of very fine
wire The coil resistance, though low, nevertheless consumes significant power with the accompanying generation of heat. When a plurality of electromagnetic relays are incorporated in a matrix switch configuration, power consumption and heat generation becomes substantial. This is particularly so if the relay actuated state is held by sustained coil energization. An alternative is to provide elaborate mechanisms for releasably holding the relays in their actuated states. Moreover, in large switching matrices the number of wiring interconnections between relays becomes very large, rendering manufacture involved and expensive.
Recent improvements in piezoceramic materials have made piezoelectric relays an attractive alternative to their electromagnetic counterparts. Piezoelectric relay drive elements may be batch fabricated from a number of different polycrystalline ceramic materials such as barium titanate, lead zirconate titanate, lead metaniobate and the like, which are precast and fired into a variety of desired shapes, such as rectangular-shaped, thin plates. Piezoelectric relays require very low actuating power, dissipate minimal power to hold an actuated state without outside assistance, and draw no current while in their quiescent state. Consequently, piezoelectric relays generate miniscule heat. They can be implemented in smaller physical sizes than comparably rated electromagnetic relays and require fewer, far simpler component parts. The electrical characteristics of piezoelectric drive elements are basically capacitive in nature and thus, unlike electromagnetic relays, are immune to stray magnetic fields.
A principal object of the present invention is to provide an improved matrix switch.
An additional object is to provide an improved matrix switch having particular, but limited application to the telecommunications field.
A further object is to provide a matrix switch of the above character utilizing piezoelectric switch actuating elements.
Another object is to provide a piezoelectric relay switching matrix utilizing an array of piezoelectric relays efficiently arranged in a compact matrix assembly.
Yet another object is to provide a piezoelectric relay switching matrix of the above-character which is amenable to batch fabrication utilizing printed circuit wiring techniques.
An additional object is to provide a piezoelectric relay switching matrix of the above-character, wherein printed circuit wiring of the matrix switch points is achieved without wiring cross-overs.
A further object is to provide a piezoelectric relay switching matrix of the above-character, wherein a minimum number of switch terminals is required.
Another object is to provide a piezoelectric relay switching matrix of the above-character which is efficient in design, convenient to manufacture, compact in size and reliable in operation over a long lifetime.
Other objects of the invention will in part be obvious and in part appear hereinafter.